Levofloxacin is a broad spectrum synthetic antibiotic. Levofloxacin is the S-enantiomer of the racemate, ofloxacin, a fluoroquinolone antimicrobial agent. The antibacterial activity of ofloxacin resides primarily in the S-enantiomer. The mechanism of action of levofloxacin and other fluoroquinolone antimicrobials involves the inhibition of DNA gyrase (bacterial topoisomerase II), an enzyme required for DNA replication, transcription repair and recombination. Levofloxacin is available as LEVAQUIN® which may be orally administered or administered intravenously.
Levofloxacin is a chiral fluorinated carboxyquinolone. Its chemical name is (S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de]-1, 4-benzoxazine-6-carboxylic acid CAS Registry No. 100986-85-4). The chemical structure of levofloxacin is shown in Formula I. Unless otherwise indicated, the terms “levofloxacin” and “levofloxacin forms” include the salts, hydrates, solvates and physiologically functional derivatives of levofloxacin. The terms also include all polymorphous forms of levofloxacin to the extent that they are not considered to be salts, hydrates, solvates or physiologically functional derivatives of levofloxacin.

U.S. Pat. No. 4,382,892 is directed toward pyrido[1,2,3-de][1,4]benzoxazine derivatives and methods of preparing them.
U.S. Pat. No. 5,053,407 is directed toward optically active pyridobenzoxazine derivatives, processes for preparing the same, and intermediates useful for preparing such derivatives.
U.S. Pat. No. 5,051,505 is directed toward processes for preparing piperazinyl quinolone derivatives. The process comprises reacting dihaloquinolones with piperazine derivatives and tetraalkyl ammonium halides in the presence of a polar solvent such as acetonitrile, dimethylformamide, pyridine, sulfolane and dimethyl sulfoxide.
U.S. Pat. No. 5,155,223 is directed toward the preparation of quinolinecarboxylic acids.
U.S. Pat. No. 5,545,737 discloses selectively producing a levofloxacin hemihydrate or monohydrate by controlling the water content of an aqueous solvent in which levofloxacin is dissolved during a crystallization. Arutla et al., Arzneimittelforschung (October 1998) 48(10):1024-7, asserts that the racemic mixture ofloxacin has an antioxidant property. One disadvantage of the prior art methods for purifying levofloxacin is that they often produce an unsatisfactory yield. For example, 45-65% yields are typical. There remains a need for novel methods for purifying levofloxacin, particularly purified preparations having diminished impurities, such as anti-levofloxacin, desmethyl levofloxacin, N-oxide levofloxacin, desfluoro-levofloxacin and/or decarboxy-levofloxacin.